“…A composition of two or more distinct cloud infrastructures (private, community, or public) that remain unique entities, but are bound together by standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load balancing between clouds).”

This definition comes from the National Institute of Standards and Technology’s Cloud Computing Synopsis and Recommendations — the same crew that determines how the Federal government undertakes its shift to the Cloud. So the NIST’s view of Cloud computing — and its recommendations — have enormous impact.

The NIST points out that hybrid Clouds — which have five variants and numerous possible configurations — can be “highly useful” but also “extremely complex.” No doubt we’ll be hearing about this complexity in coming years, since the performance, reliability, and security properties of hybrid variants can be quite different. In addition, many Cloud interoperability issues have yet to be worked out.